Finned subcaliber projectile

ABSTRACT

The technical area of the present invention relates to an anti-tank weapon comprising a finned projectile of the arrow type and a launching shoe. 
     The projectile of the invention comprises a shoe 2 the rear portion of which has fins 10 provided with pins 11 which rest against the compression cone 7 of the tube of the weapon. These fins make it possible to obtain practically constant compressive pressure and assure a proper guidance of the projectile during the barrel phase. 
     Application to the field of armaments.

This is a continuation of application Ser. No. 300,107 filed Sept. 8,1981, now abandoned.

The present invention relates to an anti-tank weapon comprising a finnedprojectile of the arrow type and a launching shoe.

In order to fire this type of ammunition under good conditions, theprojectile must be held stationary in the tube of the weapon until agiven threshold of the pressure of the propulsion gases has beenreached, this threshold corresponding to the so-called forcing pressure.When this pressure is reached the movement of the projectile commences.This forcing pressure is one of the important parameters in internalballistics, determining on the one hand the uniformity of the pairing ofpressure of the combustion gases and initial velocity of the projectileand on the other hand the constancy of the muzzle pressure of the tube.The uniformity of this forcing pressure is necessary in order to obtainminimum dispersion with respect to the fire precision.

Forcing in the case of subcaliber kinetic-energy projectiles, which canbe fired by means of a smooth tube, is at present effected in twodifferent ways, depending on the nature of the case on which theprojectile is mounted. When utilizing a metal case, the forcing isobtained by the crimping of the case on the shoe of the projectile. Thistechnique is illustrated in U.S. Pat. No. 3,107,615 and French Pat. No.2,331,771 which show the crimping of the case on a groove in the shoe ofthe projectile.

In the Example where projectiles are mounted on a combustible case, theforcing is produced by the friction of the sealing and guide bands ofthe shoe within the tube. Thus the forcing pressure is reached when theforces produced by the pressure of the gases overcome the frictionalforces.

Whatever the technique employed, it is difficult to precisely controlthe elements which make it possible to obtain a substantially constantforcing pressure for a batch of ammunition. As a matter of fact, thecrimping of the case on the projectile cannot be effected in a highlyreproducible manner since there is permanent deformation of the case asa function of machining processes and of the grade from metal of whichthe case is manufacturing. When using combustible cases, the constancyof the forcing pressure depends, on the one hand on the nature of thesealing system, which is a function of the finish of the surface and thedimensional tolerances with respect to the band-tube pairing and on theother hand, the extent on wear of the tube or barrel of the weapon.While the dimensions can be easily controlled, the same is not true withrespect to the finish of the surface of the tube which in order to be ofa constant quality, requires particular care throughout the course ofmanufacturing.

The object of the present invention is to provide an effective solutionfor the forcing problems by eliminating the drawbacks of the knowntechniques, thereby reducing the dispersions in the forcing pressure andconsiderably improving the ballistic precision of the firing by assuringuniformity in the pairing of pressure of the combustion gases andinitial velocity of the projectile and the constancy of the pressure atthe muzzle of the tube of the weapon.

Another advantage resides in the fact that this type of solution permitseasy mounting of the projectile in the case, while favoring the holdingthereof.

The mounting, in accordance with the invention, advantageously makes itpossible to reduce dispersion in the forcing pressure, even when thefiring is effected from a worn tube.

The device of the present invention also makes it possible to providemeans which assure the precise guidance of the projectile during thebarrel phase, assuring its stability and contributing to the improvementin the precision of firing.

The object of the invention is therefore an antitank ammunitioncomprising:

a finned subcaliber kinetic energy,

a launching shoe comprising a tubular portion which clamps onto theprojectile and is used in the barrel phase for the guidance andpropulsion of the projectile,

and a case containing the propellant charge and on which the launchingshoe is fastened, this ammunition coming into position resting against aforcing cone.

This weapon is characterized by the fact that the shoe comprises, incombination with the tubular portion, a front portion of the samecaliber as the tube of the weapon, which permits guidance and tightnessbetween the combustion chamber and the front of the tube, and a rearportion resting against the forcing cone and having recesses whichpermit the passage of the propulsion gases towards the forward portionof the shoe.

In another embodiment, the rear portion consists of at least two finsrigidly connected with the tubular portion of the shoe and the free endsof which rest against the forcing cone. The rear portion may also havethree fins.

The ammunition in accordance with the invention is also characterized bythe fact that the free end of the rear portion of the shoe has pins ofdeformable material which rest against the forcing cone.

When the ammunition has a non-combustible case, the case comprises theforcing cone and the rear portion of the shoe resting against said cone.

In a preferred embodiment and in the event that the ammunition comprisesa combustible case, the pins arranged at the free end of the rearportion of the shoe come against the forcing cone of the tube throughthe case.

Other characteristics and advantages of the invention will becomeevident from the following detailed description read, with reference tothe accompanying drawings which show various embodiments by way ofillustration and not of limitation.

In the drawings:

FIG. 1a is a partial longitudinal section through a first embodiment ofthe projectile of the invention,

FIG. 1b shows a detail of the rear portion of the projectile of FIG. 1on a larger scale,

FIG. 1c is a cross section along the line I.I. of FIG. 1a,

FIG. 2a is a partial longitudinal section through the rear portion of asecond embodiment.

FIG. 2b is a cross section along the line II.II. of FIG. 2a,

FIG. 2c is a section along the line III.III. of FIG. 2b,

FIG. 3a is a partial longitudinal section through a third embodiment ofa projectile in accordance with the invention,

FIG. 3b is a cross section along the line IV.IV. of FIG. 3a.

FIG. 3c is a partial section through another variant, which can be usedwhen the case is of a noncombustible material.

FIG. 1a shows a finned kinetic-energy projectile 1 driven during thebarrel phase by a shoe 2 consisting of three shells 2a, 2b and 2c. Atthe outlet of the tube, the three shells are separated from theprojectile because of the effect of aerodynamic forces, thus releasingthe projectile from the three shells 2a, 2b and 2c. The driving of theprojectile by the shoe is effected by known means such as threads 3 orgrooves and tenons arranged on the interface of the projectile and theshells. The projectile is held in a case 4 which contains the propulsivecharge and which, in this first embodiment, is a combustible material.In this figure, the ammunition is shown in place in the tube 5 of theweapon, which comprises the housing 6 of the case, the forcing cone 7and the launching tube 8 proper. In this case, as the ammunition to befired is stabilized by the fin assembly, the tube is not rifled, or isonly slightly rifled.

The shoe 2 comprises a thrust plate 21 of the caliber outside diameterand a tubular portion 22 clamping the arrow and on which three fins 10are fastened. The thrust plate 21 has a circular groove 9 within whichthere is arranged a suitable gasket which avoids leakages of propulsiongas during the internal ballistic phase. The lower ends of the fins 10are attached to the tubular portion 22 while the free ends are providedwith pins 11 which rest against the forcing cone 7 and pass through thecase 4 (FIG. 1b). These pins consist of a deformable material, such asfor instance filled or unfilled polyamides, copper or alloys. In thisfirst embodiment, each shell 2a, 2b or 2c is provided with a fin, thecontact surfaces between the shells being staggered by π/3 with respectto the fins (FIG. 1c).

FIGS. 2a, 2b and 2c show a second variant of the invention. In thisexample, the axes of symmetry 10a, 10b and 10c of the fins 10 arelocated in the planes of contact of the shells 2a, 2b and 2c. Theassembling of these various parts is effected by means of clips 12intended to break during the intermediate ballistic phase, thusfacilitating the elimination of the shoe.

The pins 11 pass through the combustible case 4 in the same manner as inthe preceding embodiment.

The assembling of the projectile and the case is effected by frontloading the projectile into the case. The pins 11 are fastened throughthe holes 14 when the projectile is in position in the case. Thissolution affords the advantage of maintaining the projectile very firmlyin the sleeve in view of the long length between the pins and the frontportion of the case on the thrust plate 21. The projectile beingmounted, the spaces between the case and the pins are filled in, thusassuring a tight packing of the propulsive charge.

FIGS. 3a and 3b show another variant of the invention in the event thatthe case used is metallic.

The forcing cone 7, which in the preceding examples was developeddirectly in the tube of the weapon, is now included within the case theinside diameter of the front end of which is at caliber, which assurescontinuity of the guidance of the projectile during the barrel phase onthe portion 13 of the tube.

In this example, the ammunition may be assembled in two ways. A firstmethod consists in introducing the complete projectile through the rearportion of the case, the latter being developed in two parts. In thecase of a monoblock case, the projectile can be mounted via the frontportion of the case provided that it is without pins 11, which are thenfastened on the fins when the projectile is positioned in length. Thepassing of the pins takes place through the holes 14 provided in thecase, which holes are closed after rotation of the projectile through anangle of about π/3 around its axis 15 in the direction indicated by thearrow 16 (FIG. 3b). The projectile is then rigidly secured to the caseat the level of the thrust plate by crimping or bonding, effected insuch a manner that upon the departure of the shot the forces due to thecrimping or bonding are far less than those which permit the deformationof the forcing pins. This condition makes it possible to obtain constantforcing pressures which are practically independent of the manner ofattachment of the projectile to the case.

FIG. 3c shows another variant, which can be used only in the event thatthe case is of metal. The inside diameter of the front end of the caseis at caliber so as to assure continuity of the guidance of theprojectile on the portion 13 of the tube. In this particular case, theforcing is obtained by the shearing of the section 17 of the pins 11,which are implanted at the rear ends of the fins and a part of which isincluded within the wall of the case 4. The diameter 18 of the shearingsection 17 is calculated in such a manner as to reach the desiredforcing pressure. After shearing, the guidance of the rear portion ofthe shoe is effected by the rear ends of the fins. The mounting of theammunition in the case is effected in the same way as in the event thatthe sleeves are combustible (FIGS. 1a to 2c) and it offers the sameadvantages.

Operation is as follows: When the propulsive charge is initiated, gasesare generated and cause an increase in pressure within the propulsionchamber. The projectile is held stationary due to the fact that the pinsare resting against the forcing cone which is arranged either in thetube (FIGS. 1 and 2) or in the metal sleeve (FIG. 3). When the forcingpressure has been reached, the pins are deformed under the action of thethrust and clear the forcing cone releasing the projectile which ispropelled in the tube. The guidance is provided via the side surface ofthe thrust plate and by the forcing pins.

These different variants offer numerous advantages. As a matter of fact,these projectile configurations make it possible on the one hand, viathe fins, favorably to displace the forces caused by the movement of thegun tube. Thus disturbances on the projectile are decreased and firedispersion reduced. On the other hand, the fact that the forcing iseffected by means of fins and pins arranged at the rear of the launchingshoe makes it possible, as compared with the known projectiles, todisplace the thrust plate towards the front. This is of particularinterest since the propulsive charge volume is increased whichsubstantially improves the performance of this type of projectile.

We claim:
 1. Ammunition to be launched from a barrel of a weaponcomprising:a finned subcaliber-sized projectile; a combustible tubularcase surrounding a rear part of said projectile and containing apropulsive charge; at least two longitudinal shell portions togethercomprising a launching shoe for launching movement with said projectilealong a barrel of a weapon, said shoe being partially disposed withinsaid tubular case and having an inner portion in form locking engagementwith said projectile to prevent axial shifting between said shoe andsaid projectile while said shoe and said projectile are within saidbarrel but allow radial separation of said longitudinal shell portionsfrom said projectile upon exit of said shoe and said projectile fromsaid barrel; said shoe comprising a tubular middle portion extendingbetween a front portion and a rear portion of said shoe; said frontportion being disposed forward of said tubular case and beingcaliber-sized to create a seal between a combustion chamber and a frontpart of said barrel of said weapon; said rear portion having recesses topermit passage of propulsive gases toward said front portion and havingabove caliber-sized projections extending through holes in said tubularcase to frictionally engage a forcing cone of said barrel, thefrictional engagement between said projections and said forcing conebeing such as to limit movement of said shoe during launch until saidpropulsive gases reach a forcing pressure.
 2. The ammunition of claim 1,wherein said rear portion of said launching shoe comprises at least tworadial fins having pins at the outer ends thereof extending through saidtubular case, said pins comprising said above caliber-sized projections.3. The ammunition of claim 2, wherein said pins are comprised of adeformable material such that said pins will deform to allow movement ofsaid shoe when said propulsive gases reach said forcing pressure.
 4. Theammunition of claim 2, wherein said longitudinal shell portionscomprising said launch shoe contact each other along a longitudinal axisof symmetry of said radial fins.
 5. The ammunition of claim 4, whereinsaid longitudinal shell portions are held together by clips.
 6. Theammunition of claim 5, wherein said clips are designed to break duringan intermediate ballistic phase.
 7. Ammunition to be launched from abarrel of a weapon comprising:a finned subcaliber-sized projectile; anon combustible tubular case surrounding a rear part of said projectileand containing a propulsive charge; at least two longitudinal shellportions together comprising a launching shoe for launching movementwith said projectile along a barrel of a weapon, said shoe beingpartially disposed within said tubular case and having an inner portionin form locking engagement with said projectile to prevent axialshifting between said shoe and said projectile while said shoe and saidprojectile are within said barrel but allow radial separation of saidlongitudinal shell portions from said projectile upon exit of said shoeand said projectile from said barrel; said shoe comprising a tubularmiddle portion extending between a front portion and a rear portion ofsaid shoe; said front portion being disposed forward of said tubularcase and being caliber-sized to create a seal between a combustionchamber and a front part of said barrel of said weapon; said rearportion having recesses to permit passage of gases toward said frontportion and having above caliber-sized projections to frictionallyengage a forcing cone of an internal surface of said tubular case, thefrictional engagement between said projections and said forcing conebeing such as to limit movement of said shoe during lauch until saidpropulsive gases reach a forcing pressure.
 8. The ammunition of claim 7,wherein said rear portion of said launching shoe comprises at least twofins having pins at the outer ends thereof, said pins comprising theprojections which frictionally engage said forcing cone.
 9. Theammunition of claim 8, wherein said pins are comprised of a deformablematerial such that said pins will deform to allow movement of said shoewhen said propulsive gases reach said forcing pressure.
 10. Theammunition of claim 8, wherein said longitudinal shell portionscomprising said launch shoe contact each other along a longitudinal axisof symmetry of said radial fins.
 11. The ammunition of claim 10, whereinsaid longitudinal shell portions are held together by clips.
 12. Theammunition of claim 11, wherein said clips are designed to break duringa intermediate ballistic phase.
 13. Ammunition to be launched from abarrel of a weapon comprising:a finned subcaliber-sized projectile; anon-combustible tubular case surrounding a rear part of said projectileand containing a propulsive charge; at least two longitudinal shellportions together comprising a launching shoe for launching movementwith said projectile along a barrel of a weapon, said shoe beingpartially disposed within said tubular case and having an inner portionin form locking engagement with said projectile to prevent axialshifting between said shoe and said projectile while said shoe and saidprojectile are within said barrel but allow radial separation of saidlongitudinal shell portions from said projectile upon exit of said shoeand said projectile from said barrel of said weapon; said shoecomprising a tubular middle portion extending between a front portionand a rear portion of said shoe; said front portion being disposedforward of said tubular case and being caliber-sized to create a sealbetween a combustion chamber and a front part of said barrel of saidweapon; said rear portion having recesses to permit passage ofpropulsive gases toward said front portion and having projectionsextending at least partially through hole in said tubular case to limitmovement of said shoe during launch until said propulsive gases reach aforcing pressure, said projections shearing at an inner surface of saidtubular case to allow movement of said shoe when said propulsive gasesreach said forcing pressure.
 14. The ammunition of claim 13, whereinsaid rear portion of said launching shoe further comprises at least tworadial fins having pins at the outer ends thereof, said pins comprisingsaid projection extending at least partially through said tubular case.15. The ammunition of claim 14, wherein said pins are comprised of adeformable material such that said pins will deform to allow move mentof said shoe when said propulsive gases reach said forcing pressure. 16.The ammunition of claim 14, wherein said longitudinal shell portionscomprising said launch shoe contact each other along a longitudinal axisof symmetry of said radial fins.
 17. The ammunition of claim 16, whereinsaid longitudinal shell portions are held together by clips.
 18. Theammunition of claim 17, wherein said clips are designed to break duringan intermediate ballistic phase.